/Engine/Source/Runtime/PreLoadScreen/Public/PreLoadSettingsContainer.h
Maps the given font file to the given language and stores it under the FontIdentifier. Identifier maps the entire CompositeFont, so if you want to add multiple fonts for multiple languages, just store them all under the same identifer
virtual void BuildCustomFont ( const [FString](API\Runtime\Core\Containers\FString) & FontIdentifier, const [FString](API\Runtime\Core\Containers\FString) & Language, const [FString](API\Runtime\Core\Containers\FString) & FilePath )